The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Order (2 members)
- Organisation (2 members)
- Organising (2 members)
- OwnCloud (1 member)
- Oxford University Press (2 members)
- P. G. Wodehouse (1 member)
- PDF (1 member)
- PEAR (2 members)
- PHP (10 members)
- PLUG (1 member)
- PVA glue (2 members)
- Pages using deprecated source tags (7 members)
- Pages with script errors (3 members)
- Pages with syntax highlighting errors (6 members)
- Painting (1 member)
- Paperwork (2 members)
- Paranoid android (2 members)
- Parlapa (2 members)
- Passwords (1 member)
- Paths (1 member)
- Peak oil (1 member)
- Pecl (1 member)
- Penguin Classics (2 members)
- People (8 members)
- Permanence (1 member)
- Personal email archiver (1 member)
- Perth (5 members)
- Perth Heritage Days (2 members)
- Perth Linux Users Group (1 member)
- Peter Lawrence (1 member)
- Philosophical Transactions of the Royal Society (2 members)
- Philosophy (2 members)
- Phoebe Ayers (1 member)
- Photo maintenance (1 member)
- Photographs (4 members)
- Photography (12 members)
- Photos (5 members)
- Photos with no known author (0 members)
- Category:PHP (0 members)
- PhpFlickr (2 members)
- Phpcs (1 member)
- Phpunit (1 member)
- Physicality (2 members)
- Piccadilly Jim (1 member)
- Pink Dandelion (2 members)
- Piwigo (5 members)
- Place (13 members)
- Placeblogging (7 members)
- Planes (1 member)
- Planet Freo (12 members)